Field of the Invention
The present invention relates to an exposure apparatus, an alignment method, and a device manufacturing method.
Description of the Related Art
An exposure apparatus is a device which exposes a substrate (a wafer or the like on the surface of which a resist layer is formed) via the pattern of an original plate (a reticle or the like) in a lithography process included in a manufacturing process of semiconductor devices or liquid crystal display devices or the like. With this type of exposure apparatus, prior to actual exposure, so-called alignment is conducted wherein an irradiation region of a pattern image and a predetermined exposure region on a substrate are aligned. As an alignment method, there is a method which sequentially conducts a first alignment process that is called, for example, mechanical pre-alignment, and a second alignment process that is called, for example, TV pre-alignment, and that has a higher degree of accuracy than the first alignment process. As a specific instance enabling application of the first alignment process of these, Japanese Examined Patent Application No. 05-030304 discloses a method wherein a shape of a notched area existing at the outer periphery of a substrate is detected using multiple linear image sensors, and alignment is conducted so that the detection result falls within a prescribed range. On the other hand, as a specific instance enabling application of the second alignment process, Japanese Unexamined Patent Application No. 2005-167002 discloses a method wherein alignment is conducted by detecting a mark that has been pre-exposed on a substrate. Japanese Unexamined Patent Application No. 2005-167002 also describes countermeasures for the case where the mark cannot be detected.
Particularly with respect to the first alignment process, with the method disclosed in Japanese Unexamined Patent Application No. 2005-167002, it may happen that alignment cannot be conducted when foreign matter (dust, protrusion of the resist, etc.) or chipping exists at a position detected by a linear image sensor, because the detection result does not fall within the prescribed range. In such cases, the productivity of the exposure apparatus is reduced, because a set of processes is temporarily suspended in the first alignment process.